1. Field of the Invention
An aspect of the present invention generally relates to a method of robustly processing and transmitting a digital broadcasting transport stream (TS), digital broadcasting transmission and reception systems, and signal processing methods thereof. More particularly, an aspect of the present invention relates to a method of robustly processing and transmitting the digital broadcasting TS, the digital broadcasting transmission and reception systems, which aim at the reception performance improvement of the ATSC VSB scheme, which is the U.S.A. terrestrial DTV system, through the information exchange and the mapping with respect to a dual TS including a normal stream and a turbo stream.
2. Description of the Related Art
The Advanced Television System Committee (ATSC) vestigial sideband (VSB) scheme, which is terrestrial digital broadcasting system used in the U.S.A., employs a single carrier and a field sync signal of 312 segments. Thus, reception performance of the broadcasting system deteriorates in a poor channel, specifically, in a doppler fading channel.
FIG. 1 is a block diagram of a transmitter and a receiver according to the ATSC DTV standard, which is the typical U.S.A. terrestrial digital broadcasting system. The digital broadcasting transmitter of FIG. 1 is the EVSB system suggested by Philips, and constructed to generate and transmit a dual stream in which robust data is added to normal data of the existing ATSC VSB system. 
As shown in FIG. 1, the digital broadcasting transmitter includes a randomizer 11, which randomizes the dual stream, a Reed-Solomon (RS) encoder 12, which is a concatenated coder type to add a parity byte to the TS to correct errors occurring due to the channel characteristics in the transmission, an interleaver 13, which interleaves the RS-encoded data in a certain pattern, and a trellis encoder 14, which trellis-encodes the interleaved data at a 2/3 rate and maps to 8-level symbols. The digital broadcasting transmitter carries out the error correction coding with respect to the dual stream.
The digital broadcasting transmitter also includes a multiplexer 15 and a modulator 16. The multiplexer 15 inserts a field sync signal and a segment sync signal to the data which is passed through the error correction coding process and hardware, as shown in data format of FIG. 2. The modulator 16 inserts a pilot tone by adding a certain DC value to the data symbol having the inserted segment and field sync signals, performs the VSB modulation by the pulse shaping, up-converts it to a signal of a RF channel band, and transmits it.
According to the dual stream scheme which transmits the normal data and the robust data through a single channel, the normal data and the robust data are each multiplexed (not shown) and fed to the randomizer 11. The input data is randomized at the randomizer 11, the randomized data is outer-coded at the RS encoder, which is an outer coder, and the coded data is spread out at the interleaver 13. The interleaved data is inner-coded by 12 symbols at the trellis encoder 14. After the inner-coded data is mapped to 8-level symbols, the field sync signal and the segment sync signal are inserted. Next, the data is VSB-modulated by inserting the pilot tone, converted to the RF signal, and transmitted.
Meanwhile, the digital broadcasting receiver of FIG. 1 includes a tuner (not shown), which converts the RF signal received through the channel to a baseband signal, a demodulator 21, which performs the sync detection and the modulation with respect to the converted baseband signal, an equalizer 22, which compensates for channel distortion with respect to the demodulated signal, a viterbi decoder 23, which corrects error of the equalized signal and decodes to symbol data, a deinterleaver 24, which rearranges the data spread by the interleaver 13 of the digital broadcasting transmitter, a RS decoder 25, which corrects errors, and a derandomizer 26, which outputs a MPEG-2 TS by derandomizing the data corrected by the RS decoder 25.
Accordingly, the digital broadcasting receiver of FIG. 1 restores the original signal by  down-converting the RF signal in the reverse operation of the digital broadcasting transmitter, demodulating and equalizing the converted signal, and performing the channel decoding.
FIG. 2 shows a VSB data frame of the U.S.A. digital broadcasting (8-VSB) system, in which the segment sync signal and the field sync signal are inserted. As shown in FIG. 2, one frame includes 2 fields, and one field includes a field sync segment, which is the first segment, and 312 data segments. In the VSB data frame, one segment corresponds to one MPEG-2 packet, and one segment includes a 4-symbol segment sync signal and 828 data symbols.
As shown in FIG. 2, the sync signals, which include the segment sync signal and the field sync signal, are used for the synchronization and the equalization of the received RF signal at the digital broadcasting receiver. That is, the field sync signal and the segment sync signal are known to the digital broadcasting transmitter and the digital broadcasting receiver, and used as a reference signal when the receiver carries out the equalization.
The U.S.A. terrestrial digital broadcasting system of FIG. 1, which is constructed to generate and transmit the dual stream by adding the robust data to the normal data of the existing ATSC VSB system, transmits the existing normal data together with the robust data.
However, the U.S.A. terrestrial digital broadcasting system of FIG. 1 cannot improve the poor reception performance in the multipath channel according to the existing normal data stream transmission although the dual stream is transmitted with the added robust data. That is, the U.S.A. terrestrial digital broadcasting system is disadvantageous in that the reception performance is not improved according to the improved normal stream. Additionally, the robust-processed turbo stream does not improve the reception performance greatly in the multipath environment. Additionally, because only one robust stream is processed at a time, the system cannot be adapted to an enhanced broadcasting business model which uses multi-turbo streams.